The problem with a smooth development process is that every day is pretty
much the same as the last. You might be writing great code and solving
interesting problems with other passionate people, but constantly
working on the same thing can begin to feel dull or even frustrating. By
having a silky-smooth development process with reliable code and regular releases,
you've removed those natural peaks and troughs, like the high of fixing another
critical bug in production before you head home and crash.
I think it was Steve Freeman
who once mentioned that sometimes it's valuable to put some of those peaks
and troughs back in, but preferably without putting critical bugs back in.

For instance, I like the idea of spending one day a week
working on unprioritised work. It might be that the developers are keen to try
out a new rendering architecture that'll halve page load times, or that
there's a piece of code that can be turned into a separate library that'll
be useful on other projects. Maybe there's a little visual bug that's never
going to be deemed important enough to be prioritised, but a developer
takes enough pride in their work to spend half an hour fixing it. This feels like
a peak to me: there's a lot of value to the product in polishing
the user experience, in refactoring the code, and trying out risky ideas, and
the developers get to scratch some of their own itches.

However, it's regularity can make it feel routine, and you're still working
on the same product. As useful as these small, regular peaks and troughs are, I think
you also need the occasional Everest. Maybe it's saying “This week, I'm going
to try something I've never tried before that's completely unrelated to the
project”. Or perhaps you need a Grand Canyon: “Today, we're just going to
concentrate on being better programmers by doing a code retreat”.
Finding something that works is hard, and you can't even reuse the same idea
too much without risking its value as an artificial peak or
trough. But I think it's important to keep trying. You don't just want a project
and its team to be alive: you need them to be invigorated.